KR100893325B1 - Metering solenoid valve for a fuel injector - Google Patents

Abstract

The metering servovalve 7 comprises a valve body 8, an open / close element 48, and an electromagnet 29 and is housed in the shell 2 of the injector 1. The electromagnet 29 is defined by an arrest element 36, which is carried by an electromagnet 29 fixed to the shell 2 by a threaded ringnut 69, which is housed in the casing 53. Actuate a mobile armature 31 for the movement to be made. The ringnut 69 is screwed with a pre-set tightening torque on the thread 71 of the shell 2. Surface 59 is transported by region 72 of casing 53 configured to undergo deformation as a function of the strong torque of ringnut 69 so as to fine tune the movement of armature 31.

Metering servovalve, ringnut, open / closed element, casing

Description

Metering solenoid valve for a fuel injector

1 is a partial cross-sectional view of a fuel injector with an adjustable metering servo valve in accordance with the present invention.

2 is an enlarged detail of FIG. 1;

* Description of the symbols for the main parts of the drawings *

1: injector 2: shell

7: metering servo valve 8: valve body

29: electromagnet 31: armature

36: stop element 69: ringnut

The present invention relates to a metering servo valve for a fuel injector in an internal combustion engine.

As is known, the servovalve of the injector generally comprises a control chamber of a conventional control rod of the injector nozzle. The control chamber is generally provided with a calibrated hole for the outlet or outlet of the fuel which is closed by the open / close element and an outlet hole in communication with the pipe for the pressurized fuel. In general, the valve body of the servovalve is fixed on the shell of the injector, while the open / closed element is controlled by the armature of the electromagnet.

The movement and ascension of the armature determines the preparation of the response of the servovalve for both opening and closing as well as the passage of fuel through the outlet hole, thus precisely controlling the movement of the armature and / or the movement of the opening / closing element. It is necessary. Servo valves are known to have an open / closed element away from the armature, the movement of which is armed against the open / closed element in a position to close the outlet hole on the one hand and in the direction of the electromagnet on the other hand. It is defined by stopping the movement of. Adjustment of armature movement is performed using at least one rigid shim that defines the gap of the armature. The wedge can be selected from among the classes of calibrated modular shims. For possible technical reasons and economical limitations, the wedges may differ from each other by an amount not less than a machining tolerance of, for example, 5 μm. However, since the operation of adjusting the armature's movement by a discrete amount with a tolerance of 5 μm is relatively rough, the flow rate of the injector often falls within the very narrow limits required by modern internal combustion engines. It is impossible to get).

From document EP-A-0 916 843 a servovalve is known, in which an armature is guided by a sleeve carrying a stationary element of the armature in the direction of the electromagnet. The sleeve is also provided with a flange on which the elastically deformable wedge intervenes and is fixed on the shell. The electromagnet is housed in a casing, the casing is fixed on the shell of the injector by threaded ringnut, and a part operating on the aforementioned flange is provided. The wedge deforms according to the strong torque of the ringnut, and by changing the torque, it is possible to precisely adjust the movement of the armature. However, the presence of the wedge and the corresponding portion makes it relatively complicated and expensive to manufacture a servovalve.

In addition, in the known servovalve described above, the open / close element is subjected to axial thrust on the one hand by the pressure of the fuel in the control chamber and on the other hand the pressure thrust when the electromagnet is not excited. Under the action of the axial thrust of the spring pre-loaded to overcome The spring has overall dimensions and properties such that it can apply significant axial thrust, for example in the range of 70N for a fuel pressure of 1800 bar.

To reduce the pre-loading of the spring for closing the open / close element, the pressurized fuel no longer acts axially, but the open / close element is supported such that the pressure action of the fuel on the open / close element is substantially balanced. Servo valves acting in the radial direction have recently been proposed. The action of the spring and the action of the electromagnets can be reduced. Also, if the risk of sticking of the armature is negligible, then the movement of the armature can be stopped directly against the core of the electromagnet so that the remaining gap on the core of the electromagnet itself can be eliminated.

It is an object of the present invention to provide an adjustable metering servovalve that provides high reliability and limited cost and eliminates the disadvantages of servovalvees for metering fuel in accordance with known techniques.

According to the invention, this object is achieved by a metering servovalve as defined in claim 1.

In order to better understand the present invention, preferred embodiments are described herein by way of example only with reference to the accompanying drawings.

1, a fuel injector (partially shown) for an internal combustion engine, in particular a diesel engine, is indicated by one. The injector 1 comprises a shell 2 or hollow body having a side inlet 4 extending along the longitudinal axis 3 and configured to be connected to a pipe for intake of fuel at a high pressure, for example in the range of 1800 bar. do. The shell 2 ends with a nozzle (not shown) in communication with the inlet 4 through the pipe 5 and configured to inject fuel into the corresponding engine cylinder.

The shell 2 has an axial cavity 6 in which a metering servovalve 7 comprising a valve body 8 is housed and which has a small part 9 having an axial cavity 10. . The control rod 11 of the injector 1 can slide in a fluid-tight way within the cavity 10, and an open / close nozzle (not shown) for closing and opening the fuel injection nozzle. ) In a known manner. The portion 9 of the body 8 provides a central annular projection 12 coupled to the corresponding portion of the inner surface of the cavity 6. This inner surface forms a recess 14 which communicates with the inlet 4 and discharges it to another pipe 16 so that the recess 14 forms an annular chamber 17 for the distribution of fuel. The space contained between the one end surface 18 of the shaft cavity 10 and the end of the rod 11 is connected to the annular chamber 17 via a calibrated inlet hole 21 of the servovalve 7. A chamber 19 is formed for control and metering.

The main body 8 has a middle portion with a large diameter which forms a flange 22 for fastening to a corresponding portion 23 of the cavity 6. For this purpose, an externally threaded ringnut 24 engages the inner thread of the part 23 and flanges axially in a fluid tight manner with respect to the shoulder 26 formed by the part 23. Screw 22 to seal. Hermetic sealing of the annular chamber 17 with the cavity 6 is instead obtained by the annular gasket 27.

The shell 2 of the injector 1 has another cavity 28 coaxial with the axis 3, and the electromagnet 29 is configured to control the notched-disk armature 31. It is fixed. The armature 31 is made of a single piece with a sleeve 32 extending in the direction opposite the electromagnet 29 and connected with the stem 33, which in turn is made of a single piece with the valve body 8. Will be understood more clearly below. The electromagnet 29 is formed by a magnetic core 34 having a pole surface 36 which is perpendicular to the axis 3 and is flat. The magnetic core 34 has an annular cavity in which the electric coil 35 is housed, and has a shaft cavity 37 in which the spiral crimping spring 38 is housed. This spring 38 is pre-loaded to exert a thrust on the armature 31 in a direction opposite to the attractive force applied by the electromagnet 29. In particular, the spring 38 includes a washer comprising one end for resting against the disk 39 for supporting the core 34 and a block 42 for guiding the end of the spring 38. 41 has the other end acting on the armature 31 through.

The stem 33 of the valve body 8 extends along the axis 3, on the opposite side of the flange 22 with respect to the portion 9 of the valve body 8. The control chamber 19 of the servovalve 7 has a passageway for the outlet or outlet of the fuel, which is designated 43 and is made entirely within the valve body 8. The outlet passage 43 is partly formed in the flange 22 and partly in the stem 33 in a first blind stretch 44 along the axis 3 and in a second radial in the stem 33. It includes a radial stretch (46). Radial stretch 46 is set in the axial portion adjacent to the flat surface of the flange 22. This constitutes a calibrated exit hole of the control chamber 19 which sets the stretch 44 in communication with the annular chamber 47, obtained by a groove in the outer surface of the stem 33, and calibrated. Have a diameter.

The sleeve 32 has an inner cylinder surface that is joined to the side surface of the stem 33 in a substantially fluid tight manner by bonding to a calibrated diameter such as less than 4 μm or by the intervention of sealing elements. The sleeve 32 comprises a truncated conical end 48 that constitutes the open / close element of the servovalve 7.

In particular, the sleeve 32 is configured to slide axially through the stem 33 between the protruding end-of-travel position and the retracted moving end position. The protruding moving end position is for closing the radial stretch 46 of the discharge passage 43 by the opening / closing element 48, the end of which is to radiate between the stem 8 and the flange 22. It is defined by the opening / closing element 48 which bears the truncated cone-shaped part. The retracted moving end position is for opening the radial stretch 46 of the passage 43 and, with the intervention of a non-magnetic gap lamina 51, the pole surface 36 of the core 34. It is defined by stopping the armature 31 with respect to.

In the protruding moving end position, the fuel exerts a zero resultant of axial thrust on the sleeve 32 since the pressure in the annular chamber 47 acts radially on the sleeve 32, while At the retracted moving end position, the fuel passes through the annular passageway 52 between the ringnut 24 and the sleeve 32 and notches of the armature 31, the cavity 28 of the core 34. , And through the axial conduits made in the support disk 39, flow from the spin stretch 46 to the discharge or recirculation channel.

When energy is supplied to the electromagnet 29, the armature 31 is arranged in the direction of the core 34 so that the open / close element 48 opens the passage 34 of the control chamber 19 to open the servo valve ( 7) open. In this way, axial translation of the rod 11 is brought about to control the opening of the injection nozzle. When no energy is supplied to the electromagnet 29, the spring 38 causes the opening / closing element 48 to close the radial stretch 46 of the discharge passage 43 again resulting in the closing of the servovalve 7. 1, the armature 31 is returned to rest the opening / closing element 48 for a portion shaped like a cone 50 with the end of the flange 22 cut off.

The electromagnet 29 is placed on the shell 2 by a casing 53 having a substantially cylindrical shape made of brass or steel of a non-magnetic metal material, such as the non-magnetic series AISI300. It is fixed. In particular, the casing 53 has a lower portion 54 (see also FIG. 2) having an inner diameter D1 and an outer diameter D2. The portion 54 is configured to be inserted into the cavity 28 and has an outer groove 56 in which an elastic o-ring 57 is inserted. The cavity 28, together with the portion 23 of the cavity 6, forms another shoulder 58 configured to be joined by the rest surface 59 of the casing 53, with the intervention of a rigid wedge 61. do.

The casing 53 also provides a second cylinder portion 62 having a thickness smaller than the lower portion 54 and is formed of an inner annular shoulder 63. The cylinder portion 62 is configured to house the core 34 of the electromagnet 29 without any significant radial action. Finally, the casing 53 holds the rest disk 39 axially bite with respect to the core 34 and rests the pole surface 36 with respect to the shoulder 63 of the casing 53 without axial movement. It has a curved upper rim 66 to hold it. Thus, the electromagnet 29 is firmly connected to the casing 53 between the shoulders 63 and to the bent rim 66 through the disc 39 to form a single block.

The cylinder portion 62 of the casing 53 also provides an outer annular projection 67 to which the annular rim 68 of the ringnut 69 threaded therein is coupled. This ringnut 69 is screwed onto a thread 71 of the outer wall of the shell 2 to cause the surface 59 of the portion 54 to oppose the shoulder 58 of the cavity 28 of the shell 2 itself. do.

In order to perform the adjustment of movement of the armature 31 and fine adjustment of the opening / closing element 48, etc., for example within 5 μm, the difference between the module classes of the wedges 61, the rest surface 59 is It is carried by the area 72 of the casing 53 and is configured to undergo elastic deformation as a function of the strong torque of the ringnut 69. In particular, the region 72 is configured in the cylinder portion 54 of the casing 53 and is set between the annular projection 67 and the rest surface 59. Region 72 has a reduced thickness cross section 73 formed by groove 56 to allow elastic deformation by bending region 72.

In turn, the resting surface 59 comprises a flat outer portion 74 and a truncated conical inner portion that forms a front chamfer 76 made on the inner surface of the portion 54. The chamfer 76 further reduces the thickness of the cross section 73 on the one hand, and on the other hand, a large rest of the casing 53 with respect to the wedge 61, even if deformation occurs by bending the region 72. To ensure the area.

Advantageously, the outer portion 74 of the surface 59 is larger than the inner diameter D4 of the groove 56 such that the cross section 73 is set in a partially cantilever manner with respect to the groove 56 itself. It has a large inner diameter D3. Preferably, the truncated conical surface of the chamfer 76 has an inclination angle α comprised between 15 ° and 30 ° with respect to the plane perpendicular to the axis 3. Further, the chamfer 76 extends in such a way that its width 1/2 (D3-D1) is comprised between 25% and 75% of the thickness 1/2 (D2-D1) of the portion 54 of the casing 53. Can be.

The movement of the opening / closing element 48 of the servovalve 7, for example the adjustment of the lift of the armature 31, is desired by an excess within 5 μm, with the strong torque pre-set of the ringnut 69. This is done by first selecting a class of wedges 61 to enable rise of the armature 31 which approximates the range. Next, fine adjustment is performed by appropriately increasing the strong torque of the ring nut 69 to change the elastic deformation of the region 72 of the casing 53.

The change in armature 31 movement is substantially proportional to the strong torque of the ringnut 69. It is possible to change the coefficient of proportionality by changing the stiffness of the portion 73 of the portion 72 of the casing 53. This rigidity can be modified by slightly changing the inner diameter D3 of the flat portion 74 of the rest surface 59 of the casing 53.

Control the angle at which the ringnut is tight (especially the torque wrench generally used to tighten the ringnut), or operating parameters such as the discharge flow rate of the servovalve 7, or else the servovalve 7 The adjustment is carried out by controlling the opening speed of and the flow rate of the injector 1. In any case, in order to prevent the ringnut 69 from being accidentally screwed out in time after the upward adjustment of the armature 31, for reasons of stability, for example, by means of an electrical-welding spot, the shell 2 It is possible to block the ring nut 69 on

From the above description, the advantages of the adjustable metering servovalve 7 according to the invention over the prior art are demonstrated. First of all, the need for each deformable wedge is eliminated, reducing the manufacturing cost of the injector and the warehousing cost of the parts. In addition, the number of flat surfaces to rest other parts requiring expensive mechanical operations for precision grinding is reduced. Finally, the casing 53 of the electromagnet 29 according to the invention can be applied on existing servo valves.

It will be understood that various modifications and improvements can be made to the above-described metering servovalve without departing from the claims. For example, the reduced cross section 73 can be obtained with a dedicated groove independent of what is provided for the gasket 57. In addition, the portion 72 may have an outer diameter that is greater than the outer diameter D2 of the portion 54 of the casing 53 itself.

In turn, the discharge passage 43 of the valve body 8 may have a number of radial stretches 46 which are preferably set at equal angular distances spaced from one another. Hard wedges 61 and / or gap film 51 may also be removed. In turn, the casing 53 may be composed of a cut plastic material. The resting surface 59 may curve or radiate between the portion 74 and the chamfer 76. Finally, the invention can be applied to a servovalve having an open / closed element separated from the armature of the electromagnet.

The present invention provides an adjustable metering servovalve that provides high reliability and limited cost and eliminates the disadvantages of servovalvees for metering fuel in accordance with known techniques.

Claims (10)

A metering servovalve for the fuel injector 1 of the internal combustion engine, the valve body 8 housed in the cavity 6 of the shell 2 of the injector 1 and the electromagnet 29 securely fixed to the casing 53. Open / close element 48 controlled by an armature 31 of The armature 31 is displaceable with respect to any movement between two opposing arrest elements 36,50, One of the stop elements 36, 50 50 is fixed to the valve body 8, The remaining stop element 36 is displaceable to adjust the movement, The casing 53 includes a cylindrical portion 54 having a resting surface 59 configured to engage a shoulder 58 of the shell 2, The casing 53 is fixed on the shell 2 by a ring nut 69 which engages with the annular projection 67 of the casing 53, The ringnut is screwed onto a thread 71 of the shell with a pre-set strong torque to engage the rest surface 59 with the shoulder 58, The cylindrical portion 54 is set between the annular projection 67 and the rest surface 59, The cylindrical portion 54 includes a region 72 that undergoes elastic deformation by the action of the strong torque, The rest surface 59 is formed by at least one parallel portion 74 perpendicular to the axis 3 of the shell 2 and the conical surface portion 76 with the end of the rest surface 59 cut off. Including a front chamfer, The cylindrical portion 54 includes an annular groove 56 such that the annular groove 56 is made on an outer surface of the cylindrical portion 54 to house an elastic o-ring. Become, The truncated conical surface portion 76 is disposed inward with respect to the parallel portion 74, The region 72 undergoing elastic deformation is disposed adjacent to the truncated conical surface portion 76 and is configured to be elastically deformable by bending of the region 72 so that a cross section 73 of reduced thickness is provided. ), The cross section 73 is formed between the annular groove 56 and the truncated conical surface portion 76, The parallel portion 74 has an inner diameter D3 greater than the inner diameter D4 of the annular groove 56, such that the cross section 73 is partially with respect to the annular groove 56. Metering servo valve, characterized in that it is set in a cantilever manner. The method of claim 1, The radial extension range (1/2 [D3-D1]) of the truncated conical surface portion 76 is 25% and 75 of the thickness (1/2 [D2-D1]) of the cylindrical portion 54. Metering sub-valve characterized in that composed between%. delete delete delete delete The method according to claim 1 or 2, The core 34 is associated with a supporting disk 39 and is fixed between the inner shoulder 63 of the casing 53 and the bent annular rim 66 of the casing 53, Metering servo valve, characterized in that the inner shoulder (63) is set between the annular projection (67) and the rest surface (59). The method of claim 7, wherein Metering characterized in that the rest surface 59 engages the shoulder 58 of the shell 2 with the intervention of a calibrated wedge 61 selected between the classes of modular shims. Servo valve. The method according to claim 1 or 2, A control chamber 19 in communication with the outlet passage 43, wherein the armature 31 has a single piece having a sleeve 32 that can slide on a stem 33 of the valve body 8. metering servo valve, characterized in that the stem (33) has at least one calibrated radial stretch (46) of the outlet passage (43). The method of claim 9, The valve body 8 is secured to the shell 2 by another threaded ringnut 24 and has a truncated conical portion 50 for stopping the closing movement of the armature 31. And the sleeve (32) comprises an end (48) configured to stop in a fluid tight manner against the truncated conical portion (50).

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